A touch panel or touch screen is one of the major interfaces between human and machine, and as a recognition device, can ingeniously combine input and display interfaces, and therefore has the advantages of saving device space and user-friendly operation. Nowadays it has been generally applied to a wide variety of consuming or industrial electronic products. For example, PDAs (Personal Digital Assistant), palm-sized PCs (Personal Computers), tablet computers, mobile phones, handwriting input devices for a smart phone, IAs (Information Appliances), ATMs (Automated Teller Machines) and POS (Points-of-Sale), etc., which can generally be seen in various occasions of business and industry applications.
With the touch panel widely applied in a variety of electronic products, users have more need for the medium and large panel. For avoiding that wrist or palm inadvertently touches the panel, how to effectively determine the signal caused by wrist or palm and to prevent wrist or palm from interfering the detection result is the most important issue in touch technology, so user's wrist or palm can be easily placed on the panel. Moreover, water or steam could stains the touch panel in the humid environment, or the effect of temperature changes on the touch panel.
For solving said issue, updating the base signal is performed when the touch panel is non-active, and updating is not performed when the touch panel is active in the conventional method. However, the conventional method may cause a heterogeneous signal for a long time, which may be judged to be an abnormal operation, if there is palm or water stains staying on the touch panel when the touch system boots. For avoiding the abnormal operation, which is misjudged to be an object touch so an active signal is generated and updating the base signal is not performed, it needs a new method to solve the different base signal when detecting. Once the heterogeneous such as palm or water stains leaves the touch panel, it may cause the object touch misjudged if user touch the touch panel by an object such as finger or stylus.